Metal fastening and process for manufacturing the same



Patented May 39, 1933;

EDWARD nnemnera AND JOHN M. GAHAGAN, or Manrson, wrsooivsrnjnnnroa'rnn TO THE FREE use or THE GOVERNMENT AND grin rsorm or UNITED srA'rn's OF AMERICA METAL rasrnnme AND rnocnss ron MANurAorUmrm THE sAME No Drawing.

Application filed August 22, .1931. I .SerialrNo'. 558,847.

(GRANTED UNDER run ACT or MARCH 3, 1883, as ansn nanararr 30,1925; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented, may be manufactured and used by or for the Government, for governmental purposes, without payment to us of any royalty thereon.

\Ve hereby dedicate the invention herein described to the free use. of the public to take effect upon the granting of a patent to Our invention consists of a microscopic pit-tin or etching of metal fastenings to such an extent as to cover their surfaces with minute indentations, the purpose of the pitting being to promote better contact between the fastening and the wood and hence increase the resistance to withdrawal. This is very desirable since the resistance to withdrawal of a fastening from wood or other material depends largely upon the nature and extent of this area of contact.

To the unaided eye the pitted surface we have invented appears the same as the original in that there is no apparent roughening. In fact, the surface may be considered smoother than the original, which, as a rule, is considerably roughened in manufacture.

Treatments hereto-fore proposed for increasing the holding power of nails and other fastenings consist either of a surface coating or a grossly roughened surface produced either by mechanical or chemical action. The coatings have the distinct disadvantage that they may be removed in handling or driving, or their effectiveness may be otherwise lost through disintegration with time. The roughened surfaces that are produced by sand blasting, barbing, or by gross pitting of any sort, tend to reduce the area and intimacy of contact between the fastening and the woodfibers,

which is so essential to high holding power and which is fully developed by the microscopically pitted surface that we have invented.

The mechanism of the process used in obtaining this surface pitting effect is extreme- 1y simple. It is as follows:

(1) The fastening is subjected to the action of water'solution's of ferric chloride which-is present a salt of some other metal,-

but more specifically with the chloridesalt i of a metalfalling below iron in the :fele'ct'ro chemicalseries;: (2) the fastening is withdrawn from the'solution' and allowed to dry in a warm atmosphere;@(3) the fastening is subjected to'ian atmosphere whose tempera ture and humidity are under control. Experience has shown satisfactory results at temperatures of about 100 and humidities'of about 80 per cent; the fastening is removed this atmosphere and imme diately "immersed 'i in boiling water to fix resulting oxides adhering to-the surfaceg The following" is a specific example of a treatment wh'ichhas given excellent results for ferrousmetal fastening:

The fastening to be treated is immersed for a period of five to six seconds in 100 c. c. of a 2' percent water solution of ferrlc' chloride containing 2 g. mercuric chloride, It is then wlthdrawn and allowed to' ren ain in a warm atmosphere for 10 'minutesjso that evaporation of the greater part of the solution may be effected. The fastening is next placed in an atmosphere where the temperature is 100 'C., and the relative humidity 75 to'80' per cent.. After a period of 60 minutes-in this atmosphere, the fastening is removed and immediately immersed staples, with surfaces microscopically pitted for difierent materials or etched, as above described, gave decidedly higher values for resistance to withdrawal than were obtained with similar fastenmgs having plaln, cement-coated, or grossly roughened surfaces. The same superiority was shown by the microscopically pitted fasteners Whether they were pulled immediately after driving or after a lapse of approximately one year.

Having fully described our discovery, We claimas our inventioni y W 1. An improvement in the process of manufacturing ferrous metal fastenings io comprising subjecting such fastenings to the action of a Water solution containing 2 per cent ferric chloride and 2 per cent mercuric chloride.

2. An improvement in the process of manufacturing ferrous metal fastenings comprising immersing such fastenings in a Water solution containing 2 per cent ferric chloride and 2 percent of a salt of a metal falling below iron in the electro-chemical series, Withdrawing said fastenings from the solution and allowing them to dry in a Warm atmosphere, then subjecting the fastenings toau temperature of approximately 100 and a humidity of approximateiy 80 per cent, removing the fastenings from said temperature and immediately immersing them in boiling water to fix the resulting iron oxides adhering to the surfaces.

3. An improvement in the process of manso ufacturing ferrous metal fastenings, comprising immersing such fastenings for a. period of 6 seconds in a 2 per cent Water solution of ferric chloride, containing 2 per cent mercuric chloride, withdrawing said fastenings from the solution and allowing them to dry in a Warm atmosphere for 1C) minutes, then subjecting the fastenings to a temperature of 100 C. with a relative humidity of 80 per cent for a period of 60 minutes, removing the fastenings, "from the said temperature and immediately immc1sing them in boiling Water for 5 minutes and drying them at atmospheric temperature EDWARD BEG-LINGER. JOHN M. GAHAGAN. 

